1. Field of the Invention
The present invention relates to an automatic joining device in a material applying apparatus of a tire fabricating machine, and more particularly to a joining device (automatic splicer) for joining ends of materials cut by a bias cutter.
2. Description of the Prior Art
In a tire fabricating machine, various rubber materials are normally fed to a cylindrical drum in the form of belts. The belt-shaped material is cut into a unit length and, on the above-mentioned cylindrical drum, the front end and the rear end of the cut length of material must be joined. Among the methods of joining cord-reinforced material such as breaker, the joining of the front end and the rear end in an overlapped state (lap-joint: FIG. 7) is not favored, but in many cases the joining of the cut planar surfaces of the front and rear ends butted against each other (butt-joint: FIG. 8) is required.
Such joining was normally carried out manually, but according to the demand for automation a number of automated devices have been proposed.
In a representative device that was proposed in the prior art, as shown in FIG. 9, material 2' cut into a length somewhat shorter than the length of one turn of drum 1' is placed on a conveyor 3' for conveying materials. The material 2' is pressed against the drum 1', and butt-joining is effected by slowing down the feed speed of the conveyor relatively to the rotational speed of the drum to the extent of the aforementioned somewhat shorter length.
In addition, a method for resolving the problem of a divergence of the ends at the joining portion is disclosed in Japanese Patent Application No. 61-144968 (1986).
The invention disclosed in Japanese Patent Application No. 61-144968 (1986) will be described with reference to FIG. 10.
In FIG. 10, reference numeral 01 designates a wrapping drum, number 02 designates a wrapping surface of the wrapping drum, number 04 designates a raw material application conveyor, numeral 05 designates a raw material measuring and transporting conveyor, numeral 024 designates an automatic splicer, numerals 022 and 026 designate magnets, numeral 025 designates a slide frame, numeral 027 designates a press plate, reference character M.sub.1 designates cut raw material, reference character M.sub.2 designates a front end of the cut raw material, the reference character M.sub.3 designates a rear end of the cut raw material.
The above-described apparatus is similar to that shown in FIG. 9 with respect to the wrapping of raw material around the forming drum 01 by means of the raw material application conveyor 04, and is provided with a joining device 024 (automatic splicer) for bringing spaced ends of the material into a butted state after the wrapping thereof over the drum.
The structure of the automatic splicer 024 is shown in FIGS. 11 and 12. Two sets of guide rollers 110 are mounted to a bracket 111, and these guide rollers are adapted to be moved close to or away from the drum 01 by means of a drive cylinder 115. In addition, separately from the guide rollers 110, a splice roller 106 is mounted on a bracket 107, and this splice roll 106 is movable close to or away from the drum 01 by means of a drive cylinder 109. Both brackets 111, 107 are mounted to brackets 104 and 105, and this assembly is freely movable in the direction of the drum axis as guided by a shaft 102 via a linear bearing 103. The splice roller 106 is mounted at an angle with respect to the guide roll 110 so as to assume a diverging attitude as shown in FIG. 12.
After the material has been wrapped around the cylindrical drum surface by means of the conveyor, as shown in FIG. 13, both rollers 110 and 106 are pressed against the material so that a joining portion is located between the guide rollers 110 and the splice roller 106. Thereafter, when the drum 01 is rotated, the entire assembly is moved along the axis of the drum by the guide rollers 110. Meanwhile, the side M.sub.3 of the open-end material is drawn towards the side M.sub.2 by the action of the splice roller 106, and thus the cut planar surfaces of the respective sides are joined to each other.
With the above-described device relying upon the splice roller and the guide rollers in the prior art, the force exerted by the splice roller to narrow the gap between the respective cut ends would tend to divert the guide rollers from the direction in which they should advance. Consequently, it is difficult to move both rollers while holding the joining portion between the guide rollers and the splice roller. In addition, despite the fact that the opening width may be different in various applications, the amount of the material drawn by the splice roller is constant, and so, unless the opening width at the time of the initial wrapping is limited to a certain extent, good joining cannot be attained.
If the interval between the guide rollers and the splice roller is increased for the purpose of facilitating a position setting of the ends of the cut material, the joining of the materials becomes difficult. In practice, the roller interval is about 2-3 mm, and it is difficult to set the ends in position so that the joining portion has such an interval.